1. Field of the Invention
Embodiments described herein relate generally to magnetic resonance imaging.
2. Description of the Related Art
MRI is an imaging method which magnetically excites nuclear spin of an object (a patient) set in a static magnetic field with an RF pulse having the Larmor frequency and reconstructs an image based on MR signals generated due to the excitation. The aforementioned MRI means magnetic resonance imaging, the RF pulse means a radio frequency pulse, and the MR signal means a nuclear magnetic resonance signal.
In MRI, a fast imaging technology called parallel imaging is known. In parallel imaging, a phased array coil which includes many coil elements is used as an RF coil device set on an object so as to receive MR signals by these coil elements.
In parallel imaging, generally, wraparound artifact occurs as a result of decreasing the number of data acquisition times by thinning out a phase encode step number, and this artifact is compensated in unfolding processing. Specifically, a reference scan is separately performed so as to generate a spatial sensitivity distribution map of each of the coil elements of the phased array coil (for example, see Patent Document 1 and Patent Document 2).
The sensitivity distribution map is, for example, map data indicating how the detection sensitivity of each of the coil elements inside the phased array coil spatially to MR signals varies spatially. Then, the wraparound artifact caused by the decreased phase encode step number is compensated based on the sensitivity distribution map by an appropriate method such as expanding unfolding method (for example, see Patent Document 3).
[Patent Document 1] Japanese Publication of Patent Application No. 2007-319348
[Patent Document 2] Japanese Publication of Patent Application No. 2005-237703
[Patent Document 3] Japanese Publication of Patent Application No. 2004-329613
In conventional technology, an acquisition region of MR signals in a reference scan is (manually) selected by a user as a wide region that infallibly includes the imaging region of the main scan, in order to prevent lack of data for generating the sensitivity distribution map.
Therefore, “MRI technology to enable setting of conditions of a calibration scan without making a user consider a signal acquisition region of a calibration scan” has been desired.